1. Field of the Invention
The present invention relates generally to phasing and indicator arrangements for switchgear and the like in the field of electrical power distribution, and more particularly to an arrangement that facilitates phasing measurements with the use of conventional voltmeters and an indicating arrangement with desirable test features.
2. Description of the Related Art
In the field of electrical power distribution, it is a common practice to perform phasing measurements between various power cables to determine the phase difference between and the correct connection of the power cables throughout the system. Various prior art arrangements include indicator lights that respond to sensed voltage signals to indicate whether two signals are in phase or out of phase. For example, device types HO-MPK and HO-PV are available from ELSIC, Trompeterallee, Germany. Further, page 14 of Merlin Gerin Publication AC0063/3E illustrates voltage indicator lamps and a phase concordance unit designated MX 403.
Additionally, various devices are known that respond to voltage sensors and that function as voltage indicators. An arrangement for testing the integrity of the voltage sensing system is shown in U.S. Pat. No. 5,521,567.
While these prior art arrangements may be useful to provide various indicator and phasing arrangements, the prior phasing arrangements are rather awkward to operate, require manipulation and interconnection of various components, require relatively expensive sensing devices, require the use of specialized meters or devices, and/or require external power supplies. Further, the prior indicator arrangements require separate power supplies for testing and do not provide simplified unambiguous self-testing functions.